Elevator system design including a belt assembly with a vibration and noise reducing groove configuration

ABSTRACT

An elevator system design incorporates a belt having a jacket coating a plurality of elongate load bearing members such as steel cords. The jacket includes a plurality of spaced grooves on at least one side of the belt. The width of the grooves and the size of at least the drive sheave in the system are selected so that a ratio of the groove width to the sheave diameter is within a selected range. In one example, the ratio preferably is less than about 0.05. The grooves also preferably include a fillet at the edges of the grooves where the grooves meet with the sheave-engaging surface on the belt jacket.

This application claims priority to the International Application NumberPCT/US03/01148, which was filed on 15 Jan. 2003, which claims priorityto U.S. Provisional Application No. 60/349,057, which was filed on 16Jan. 2002.

FIELD OF THE INVENTION

This invention generally relates to elevator system design. Moreparticularly, this invention relates to an elevator system designstrategy incorporating a belt assembly having a specialized grooveconfiguration.

DESCRIPTION OF THE RELATED ART

Elevator systems typically include a cab and counterweight that movewithin a hoistway to transport passengers or cargo to different landingswithin a building, for example. A load bearing member, such as roping ora belt typically moves over a set of sheaves and supports the load ofthe cab and counterweight. There are a variety of types of load bearingmembers used in elevator systems.

One type of load bearing member is a coated steel belt. Typicalarrangements include a plurality of steel cords extending along thelength of the belt assembly. A jacket is applied over the cords andforms an exterior of the belt assembly. Some jacket applicationprocesses result in grooves being formed in the jacket surface on atleast one side of the belt assembly. Some processes also tend to causedistortions or irregularities in the position of the steel cordsrelative to the exterior of the jacket along the length of the belt.

FIG. 6, for example, illustrates both of these phenomena. As can beseen, the spacing between the exterior of the jacket 200 and the cords210 varies along the length of the belt. As can be appreciated from theillustration, the cords 210 are set within the jacket as if theycomprise a series of cord segments of equal length corresponding to thegroove spacing. The illustration of FIG. 6 includes an exaggeration ofthe typical physical cord layout for purposes of illustration. Theactual distortions or changes in the position of the cords relative tothe jacket outer surfaces may not be discernable by the human eye insome examples.

When conventional jacket application processes are used, the manner inwhich the cords are supported during the jacket application processtends to result in such distortion in the geometry or configuration ofthe cords relative to the jacket outer surfaces along the length of thebelt.

While such arrangements have proven useful, there is need forimprovement. One particular difficulty associated with such beltassemblies is that as the belt moves in the elevator system, the groovesand the cord placement in the jacket interact with other systemcomponents such as the sheaves and generate undesirable noise, vibrationor both. For example, as the belt assembly moves at a constant velocity,a steady state frequency of groove contact with the sheaves creates anannoying, audible tone. The repeated pattern of changes in the cordspacing from the jacket outer surfaces is believed to contribute to suchnoise generation.

An alternative arrangement is required to minimize or eliminate theoccurrence of vibrations or an annoying tone during elevator systemoperation. This invention addresses that need.

SUMMARY OF THE INVENTION

In general terms, this invention is an elevator system design includinga belt having a plurality of grooves that have a configuration selectedto minimize vibration and noise during elevator system operation.

An elevator system designed according to this invention includes a cabthat carries passengers or cargo between landings within a building, forexample. A belt supports the cab and facilitates movement of the cab.The belt has a plurality of spaced grooves on at least one side of thebelt. At least one sheave over which the belt travels as the cab movesincludes a diameter that is selected to have a relationship to the widthof the grooves on the belt. The ratio of the groove width to the sheavediameter is chosen to be less than about 0.05.

In one example, the ratio between the groove width and the belt diameteris selected to be between about 0.001 and 0.015.

A method of designing an elevator system according to this inventionincludes selecting a diameter of at least the drive sheave that isresponsible for moving the belt and cab within the hoistway. The widthof the grooves is then selected such that a ratio of the groove width tothe sheave diameter is less than about 0.05. The inventive belt assemblyincludes a plurality of cords extending generally parallel to alongitudinal axis of the belt. A jacket over the cords includes aplurality of grooves configured to minimize the occurrence of vibrationsand noise during elevator operation.

In another example, the grooves have fillets near the sheave-engagingsurface of the jacket. A radius of curvature of the fillets may becustomized along with other system parameters to minimize vibrations andnoise. In one example, the fillets have a radius of curvature betweenabout 0.1 mm and about 0.5 mm.

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiments. The drawings thataccompany the detailed description can be briefly described as follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a portion of an example belt assemblydesigned according to an embodiment of this invention.

FIG. 2 is a cross-sectional illustration taken along the lines 2-2 inFIG. 1.

FIG. 3 is a schematic illustration of elevator system designed accordingto an embodiment of this invention.

FIG. 4 graphically illustrates a feature of the inventive approach toelevator system design.

FIG. 5 graphically illustrates the vibration causing effects of arelationship between the dimensions of a groove width and sheavediameter.

FIG. 6 schematically shows a prior art belt.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 and 2 schematically illustrate a belt assembly 20 that isdesigned for use in an elevator system. A plurality of cords 22 arealigned generally parallel to a longitudinal axis of the belt assembly20. In one example, the cords 22 are made of strands of steel wire.

A jacket 24 covers over the cords 22. The jacket 24 preferably comprisesa polyurethane-based material. A variety of such materials arecommercially available and known in the art to be useful for elevatorbelt assemblies. Given this description, those skilled in the art willbe able to select a proper jacket material to suit the needs of theirparticular situation.

The jacket 24 establishes an exterior width and thickness of the beltassembly 20. In one example, the width of the belt assembly is 30millimeters and the thickness is 3 millimeters. In the same example, thecords 22 have a diameter of 1.65 millimeters. The cords 22 preferablyextend along the entire length of the assembly.

The jacket 24 includes a plurality of grooves 30 on at least one side 32of the jacket 24. In the illustrated example, the grooves extend acrossthe entire width of the belt assembly.

The grooves result from some manufacturing processes, many of which arewell known in the art, that are suitable for formation of the beltassembly 20. In the example embodiment of FIGS. 1 and 2, the grooveshave a configuration that is useful for reducing vibrations duringelevator system operation.

In the illustrated example, the groove configuration includes a roundededge or fillet 34 at each end of each groove where the groove joins theside 32 of the exterior of the jacket. The fillets 34 differ fromconventional groove designs where a sharp edge typically existed wherethe groove met with the exterior surface 32 of the jacket 24. A roundedfillet reduces noise and vibration as each groove contacts a sheaveabout which the belt wraps during elevator system operation.

The radius of curvature for each rounded edge or fillet 34 in theinventive arrangement preferably is selected to minimize the amount ofvibration occurring from the interaction between the belt assembly 20and other elevator system components. Various factors affecting theradius of curvature selection include the distance or spacing betweenthe grooves 30, the width W of each groove, the stiffnesscharacteristics of the jacket material and the thickness of the jacketmaterial, which typically dictates the depth of each groove. In general,it is more preferable to have a larger radius of curvature, which tendsto smooth out the transition between the side 32 of the jacket 24 andthe grooves 30. A belt incorporating the inventive fillet design willinclude a fillet radius of curvature in the range from about 0.1 mm toabout 0.5 mm. In one example, the radius of curvature for the fillets 34is about 0.2 mm. In another example the radius is about 0.4 mm.

Another benefit of the fillet 34 is that it tends to reduce thesensitivity to shearing effects as the belt assembly 20 travels over thedrive sheave 58. Because of the differing weights on the different sidesof the drive sheave, a portion of the belt assembly 20 tends to be undergreater load than the other portion on the opposite side of the drivesheave 58. This occurrence tends to introduce a shear effect on thejacket material 24. Incorporating fillets 34 on the groove 30 tends toreduce the sensitivity to this shearing effect and the contribution tovibration and noise generation during elevator system operation.

The width W of each groove 30 preferably is selected so that there is arelationship between the groove configuration and other components inthe elevator system that provides optimal noise-reducing performance.FIG. 3 schematically illustrates an example elevator system 50 includingan inventive belt assembly 20. Of course, there are other types ofelevator system arrangements that include sheaves about which ropes orbelts travel and this invention is not limited to the example systemarrangement, which is schematically shown for discussion purposes. Theelevator system 50 includes a conventional counterweight 52 and cab 54that move through a hoistway 56 in a conventional manner. The beltassembly 20 is operative to support the loads of the counterweight 52and cab 54 during system operation. The illustrated example includes adrive sheave 58 driven by a motor mechanism 60. Idle sheaves 62, 64 and66 facilitate the desired movement of the cab 54 and counterweight 52through the hoistway as needed to transport passengers or cargo betweenlandings within a building, for example.

The groove width W preferably is selected to have a dimensionalrelationship with at least the diameter of the drive sheave 58 of thesystem 50. In some situations, all sheaves within the system 50 willhave the same diameter while in others there may be sheaves of varyingsizes within the system. At least the relationship between the groovewidth W and the size of the drive sheave (or sheaves, depending on theparticular installation) is chosen to optimize the noise reducingproperties of the belt assembly 20.

In general, a larger sheave diameter is preferred as the width W of thegrooves 30 is increased. This invention includes the realization thatrelatively larger groove widths W compared to smaller sheave diameterstend to produce more vibration and noise generation than arrangementshaving a desirable dimensional relationship.

FIG. 4 graphically illustrates this phenomena in the graph 70. A firstplot 72 shows the amount of vibration occurring in an examplearrangement where the belt has dimensions consistent with the examplesmentioned above. The amount of vibration occurring when the sheavediameter is 75 millimeters is shown in the plot 72. The plot 74represents the amount of vibration occurring when the sheave diameter isincreased to 100 millimeters. The plot at 76 shows the amount ofvibration occurring when the sheave diameter is further increased to 125millimeters. Given the peak-to-peak amplitude of each of the plots 72,74 and 76, it is apparent that a larger sheave diameter for the givengroove configuration and dimensions provides the least amount ofvibration and, therefore, is the least likely to have noise generationduring elevator system operation.

One factor that must be considered when selecting a sheave diameter anda groove width W is that a smaller sheave diameter may be preferredbecause it requires less torque and a less expensive machine includingthe motor mechanism 60. On the other hand, a larger sheave tends toincrease the life of the belt assembly 20 and, according to thisinvention, tends to decrease the amount of vibration and noisegeneration during elevator system operation. Those skilled in the artwho have the benefit of this description will be able to selectappropriate dimensional relationships to meet the needs of theirparticular situation.

According to this invention, one preferred relationship between groovewidth W and sheave diameter preferably results in a ratio of the groovewidth W to the sheave diameter that is less than about 0.05. Accordingto one example implementation of this invention, when the ratio exceeds0.05, the amount of vibration is considered beyond an acceptable level.In another example, where the speed of elevator cab movement is lower, ahigher ratio may be acceptable depending on the particular elevatorsystem.

As can be appreciated from FIG. 5, as the ratio of groove width tosheave diameter increases, the amount of vibration (and noise)increases. The plot 80 in FIG. 5 shows an amplitude of vibrations on theY axis with the ratio of groove width to sheave diameter on the X axis.When the ratio is below 0.008, the amount of vibration is effectivelythe same and is considered acceptable in many situations because thatlevel of vibration does not tend to generate any audible noise withinthe elevator system. As the ratio increases from 0.008 to 0.05, theamount of vibration increases in a generally linear fashion as can beappreciated from the plot.

One preferred range for the ratio of groove width to sheave diameter isbelow about 0.008. When the term “about” is used before a parameter inthis description, it should be interpreted to include amounts varying byalmost a full unit more or less within a factor of ten. For example,“about 0.008” should be interpreted to at least include a range from0.0071 to 0.0089 and “about 0.05” should be interpreted to at leastinclude a range from 0.041 to 0.059.

A variety of ranges may be used depending on the particulars of a givenelevator system. Those skilled in the art who have the benefit of thisdescription will be able to select the best ratio to meet the needs oftheir particular situation.

By combining the relationship between the groove width W and the size ofthe sheave (i.e., sheave diameter) and incorporating fillets 34 on thegrooves 30, the inventive arrangement presents a substantial improvementin reducing vibration and noise generation during elevator systemoperation.

In some examples it is preferred to minimize the width of the grooves30. There is, however, a point where the width of the groove 30 cannotbecome any smaller because of manufacturing tolerances. This tolerancewill vary depending on the particular material selected to form thejacket 24 and the tooling used in the manufacturing process.

Additionally, it is believed that below a certain width, the noisereducing benefits of the inventive arrangement are not increased, as canbe appreciated from FIG. 5.

The particular width of each groove 30 that provides optimal noisereducing performance may also vary depending on other characteristics ofa particular elevator system, including overall belt assembly size andsheave diameter, for example. The speed of movement of the belt assembly20 within the elevator system is another factor that affects theoptimally selected groove width W. In general, according to thisinvention it is preferred to utilize ratios of groove width to sheavediameter in lower ranges for higher speed elevator systems compared tothose of lower speeds. In other words, as elevator speed increases, thepreferred ratio of groove width to sheave diameter decreases. Likewise,as elevator speed decreases, the acceptable range of ratios of groovewidth to sheave diameter increases. Those skilled in the art who havethe benefit of this description will be able to select appropriategroove width W and sheave diameter(s) to optimize the noise reducingcharacteristics within a particular installation.

The preceding description is exemplary rather than limiting in nature.Variations and modifications to the disclosed examples may becomeapparent to those skilled in the art that do not necessarily depart fromthe essence of this invention. The scope of legal protection given tothis invention can only be determined by studying the following claims.

1. An elevator system, comprising: a cab that moves at a elevator speed;a belt that supports the cab and facilitates movement of the cab, thebelt having a plurality of spaced grooves on at least one side of thebelt, each of the grooves including a fillet at an edge of each groove;and at least one sheave over which the belt travels as the cab moves,the sheave having a diameter that has a relationship to a width of thegrooves on the belt so that a ratio of the groove width to the sheavediameter is less than about 0.015, wherein the ratio of the groove widthto the sheave diameter is (i) within a first range when the elevatorspeed is above a first speed and (ii) within a second, higher range whenthe elevator speed is a second, slower speed below the first speed. 2.The system of claim 1, wherein the ratio is less than about 0.008. 3.The system of claim 1, wherein the ratio is between 0.001 and 0.015. 4.The system of claim 1, wherein the fillets each have a radius ofcurvature that is between about 0.1 mm and about 0.5 mm.